GYMNOSPORANGIUJI. 



399 



of the spot in (question is either completely destroyed or trans- 

 formed into irregular cells, separated by intercellular spaces. 



The anatomical changes in swellings (Fig. 235) induced by 

 (I. sahinac on Juiii'pcrus Sabina were investigated by Woernle 

 with the following results. Wood, bast, and rind are increased 

 round the whole circumference of the stem. Along with 

 the broadening of the year-rings, however, there occurs a 

 change in the structure of tlie diseased wood. The same 



Fig. 234. — A few leaves enlarged from Fig. 233. The leaf to left hand bears 

 pycnidia on red spots on the upper surface of the leaf ; the remaining le;ives bear 

 aecidia on raised portions of their surface. Several aecidia still furtlier enlarged 

 show the peridia dehiscing by longitudinal slits, (v. Tubcuf del.) 



tissues occur in the year-rings as already described for G. 

 clavariaeforme, viz. thickened twisted tracheids, loosely connected 

 together and with fissure-like pits ; medullary rays more 

 numerous and broader ; the limits of the year-ring difficult to 

 distinguish ; and a yellow pigment deposited in the walls of 

 all the elements. A tissue of this nature may be found round 

 the whole circumference of a twig even in the first year after 

 infection, and regularly each succeeding year. Woernle only 

 rarely found zones of irregular cell-formation like those 



